1. Field of the Invention
The present invention relates in general to a new and improved method and apparatus for reducing unwanted high frequency noise in mobile communication devices. It more particularly relates to such a new and improved method and apparatus for eliminating, or at least greatly reducing, unwanted high frequency noise, such as ground plane interference in communication devices such as mobile handsets.
2. Related Art
The related art discussed in this section is considered to be background information only, and is not regarded as prior art.
Current mobile communication devices commonly have severe design requirements for protecting certain more sensitive internal components such as oscillators, against high frequency noise. Such design requirements are oftentimes difficult to achieve for devices such as mobile handsets when attempting to deal with phase noise problems. Such noise reduction considerations can produce unwanted increases in the length of time for the design cycle.
Phase noise reduction within mobile handsets of communication devices has been a problem for designers for some applications. Oscillators within a mobile telephone are susceptible to corruption from other sources due to their close proximity with an enclosure. Such a problem becomes exacerbated with the continual shrinkage of form factors to make the handset smaller in size and more compact to use.
One of the main contributors to phase noise is an effect called “ground bounce”. This phenomenon occurs when a high-power noise-producing component such as a transmitter commences operation. Such an operation may cause a sudden in-rush of electrical current. Due to the finite resistance across the metallic or copper clad wiring board, a potential difference is thus created. As the ground return may typically be shared by many parts and components of the handset, oscillators or other noise sensitive components can be adversely affected by the potential difference, which can also be coupled into other parts of the system and thus cause unwanted interference.
In an attempt to overcome these interference problems, the de-coupling capacitors have been employed. Also, ground returns have been connected together to a single ground reference point. None of these solutions have been entirely satisfactory for certain applications.